#include <locale.h>
#include <stdlib.h>

int utf8_to_wcs(wchar_t *wcs,size_t n,const char *utf8,size_t *size){
    if (NULL == size){
        return -1;
    }
    setlocale(LC_CTYPE,"en_US.UTF-8");
    *size = mbstowcs(wcs,utf8,n);
    return 0;
}